WL#2486 - Natural/using join according to SQL:2003.

Post-review fixes according to Monty's review.


sql/item.h:
  Unite all code that stores and restores the state of a name resolution context
  into a class to represent the state, and methods to save/restore that
  state.
sql/mysql_priv.h:
  Reorder parameters so that length is after the name of a field,
  and database is before table name.
sql/sql_acl.cc:
  Reorder parameters so that length is after the name of a field,
  and database is before table name.
sql/sql_base.cc:
  * Reorder parameters so that length is after the name of a field,
    and database is before table name.
  * Added new method - Field_iterator_table_ref::get_natural_column_ref
    to avoid unnecessary code when it is knwon that no new columns will
    be created when accessing natural join columns.
sql/sql_insert.cc:
  Unite all code that stores and restores the state of a name resolution context
  into a class to represent the state, and methods to save/restore that
  state.
sql/sql_lex.cc:
  Removed obsolete comment.
sql/sql_lex.h:
  Return error from push_contex() if there is no memory.
sql/sql_list.h:
  Extended base_list_iterator, List_iterator, and List_iterator_fast with an
  empty constructor, and init() methods, so that one doesn't have to construct
  a new iterator object every time one needs to iterate over a new list.
sql/sql_parse.cc:
  Moved common functionality from the parser into one function, and renamed
  the function to better reflect what it does.
sql/sql_yacc.yy:
  Moved common functionality from the parser into one function, and renamed
  the function to better reflect what it does.
sql/table.cc:
  * Extended base_list_iterator, List_iterator, and List_iterator_fast with an
    empty constructor, and init() methods, so that one doesn't have to construct
    a new iterator object every time one needs to iterate over a new list.
  * Added new method Field_iterator_table_ref::get_natural_column_ref to be
    used in cases when it is known for sure that no new columns should be
    created.
sql/table.h:
  - column_ref_it no longer allocated for each new list of columns
  - new method get_natural_join_column for faster/simpler access
    to natural join columns.

1 files changed, 42 insertions, 14 deletions

diff --git a/sql/table.cc b/sql/table.cc
index 8068a839052..4cc94439143 100644
--- a/sql/table.cc
+++ b/sql/table.cc
@@ -2702,8 +2702,9 @@ Item *create_view_field(THD *thd, TABLE_LIST *view, Item **field_ref,
   if (view->schema_table_reformed)
   {
     /*
-      In case of SHOW command (schema_table_reformed set) all items are
-      fixed
+      Translation table items are always Item_fields and already fixed
+      ('mysql_schema_table' function). So we can return directly the
+      field. This case happens only for 'show & where' commands.
     */
     DBUG_ASSERT(field && field->fixed);
     DBUG_RETURN(field);
@@ -2735,21 +2736,14 @@ Item *create_view_field(THD *thd, TABLE_LIST *view, Item **field_ref,
 void Field_iterator_natural_join::set(TABLE_LIST *table_ref)
 {
   DBUG_ASSERT(table_ref->join_columns);
-  delete column_ref_it;
-
-  /*
-    TODO: try not to allocate new iterator every time. If we have to,
-    then check for out of memory condition.
-  */
-  column_ref_it= new List_iterator_fast<Natural_join_column>
-                     (*(table_ref->join_columns));
-  cur_column_ref= (*column_ref_it)++;
+  column_ref_it.init(*(table_ref->join_columns));
+  cur_column_ref= column_ref_it++;
 }
 
 
 void Field_iterator_natural_join::next()
 {
-  cur_column_ref= (*column_ref_it)++;
+  cur_column_ref= column_ref_it++;
   DBUG_ASSERT(!cur_column_ref || ! cur_column_ref->table_field ||
               cur_column_ref->table_ref->table ==
               cur_column_ref->table_field->table);
@@ -2876,7 +2870,6 @@ GRANT_INFO *Field_iterator_table_ref::grant()
 
   SYNOPSIS
     Field_iterator_table_ref::get_or_create_column_ref()
-    thd         [in]  pointer to current thread
     is_created  [out] set to TRUE if the column was created,
                       FALSE if we return an already created colum
 
@@ -2889,7 +2882,7 @@ GRANT_INFO *Field_iterator_table_ref::grant()
 */
 
 Natural_join_column *
-Field_iterator_table_ref::get_or_create_column_ref(THD *thd, bool *is_created)
+Field_iterator_table_ref::get_or_create_column_ref(bool *is_created)
 {
   Natural_join_column *nj_col;
 
@@ -2923,6 +2916,41 @@ Field_iterator_table_ref::get_or_create_column_ref(THD *thd, bool *is_created)
 }
 
 
+/*
+  Return an existing reference to a column of a natural/using join.
+
+  SYNOPSIS
+    Field_iterator_table_ref::get_natural_column_ref()
+
+  DESCRIPTION
+    The method should be called in contexts where it is expected that
+    all natural join columns are already created, and that the column
+    being retrieved is a Natural_join_column.
+
+  RETURN
+    #     Pointer to a column of a natural join (or its operand)
+    NULL  No memory to allocate the column
+*/
+
+Natural_join_column *
+Field_iterator_table_ref::get_natural_column_ref()
+{
+  Natural_join_column *nj_col;
+
+  DBUG_ASSERT(field_it == &natural_join_it);
+  /*
+    The field belongs to a NATURAL join, therefore the column reference was
+    already created via one of the two constructor calls above. In this case
+    we just return the already created column reference.
+  */
+  nj_col= natural_join_it.column_ref();
+  DBUG_ASSERT(nj_col &&
+              (!nj_col->table_field ||
+               nj_col->table_ref->table == nj_col->table_field->table));
+  return nj_col;
+}
+
+
 /*****************************************************************************
 ** Instansiate templates
 *****************************************************************************/